Synthesis of substituted 1, 3 diazacyclopentenes and 1, 3 diazacyclohexenes



. 2,876,223 SYNTHESIS on sunsrr'rurnn 1,3 DIAZACYCLO- PENTENES AND 1,: DIAZACYCLOHEXENES Barry M. Bloom, Jackson Heights, N. Y., assignor to Chas. Pfizer & Co., Inc., New York, N. Y., a corporation of Delaware 4 Claims. (Cl. 260-256.

'This invention is concerned with a process for the preparation of useful organic nitrogen compounds. More particularly, it is concerned with the process for the preparation of substituted and unsubstituted 2-(1,-2,3,4'- tetrahydro- 2' isoquinolyl)- 1,3 diazacyclopentenes, diazacyclohexenes and their acid addition salts. .,The freebase'sand the pharmaceutically acceptable acid addition. salts prepared, by the process of this invention are usefulras regulat'ors of the cardiovascular system as disclosed in copending applications, Serial No. 616,639 and Serial No. 616,594 filed on October 18, 1956. Acid addition salts prepared using the process of this invention and containing pharmaceutically unacceptable acids are useful for isolation of the pharmaceutically active free base and/or for the purification of the pharmaceutically active compounds. 1

In accordance ,with' the process of 'this' invention, 1,2,3,4-tetrahydroisoquinoline is reacted with a 2-alky1- thio or 2-aralkylthio-1,3-diazacyclopentene or -hexene acid addition salt, theresulting alkyl or aralkyl mercaptan removed, if desired, and the useful compound isolated either as an acid addition salt or as a free base. The reaction is illu'stratedin the following formula:

wherein R is. preferably an alkyl or aralkyl group containing up to, ten carbon atoms, X is an anion of an organic orinorganic acid giving a hydrogen ion concentration of at least 10- moles per liter in aqueous solution, and n is the integer two or three.

As stated above R is preferably an alkyl or aralkyl group. Most satisfactory results are obtained when R is an alkyl or aralkyl group which produces a volatile mercaptan, e. g. methyl, as the by product of the reaction. It is not necessary to remove the mercaptan, but if it is desired to do so itcan be readily accomplished. Volatile mercaptans simply go off as a vapor during the course of the reaction. Non-volatile mercaptans can be removed by extraction of the reaction mixture with lead acetate solution. v 1

The process of this inventionis applicable to, 1,23,4- tetrahydroisoquinolines in which carbon atoms are substituted with alkyl, alkoxy, phenyl thioalkyl, hydroxyl, mercapto, halogen, cyano, carbonyl, acylamino and other groups. It is, however, best to avoid strongly acid substituents particularly those which give tetrahydroisoquinolines having a hydrogen ion concentration of moles per liter or higher in aqueous solutions, e. g., the sulfonicor phosphonic acid groups; The carbon atoms 2,876,223 Patented Mar. 3, 1959 of a 1,3-diazacycloalkene can also be substituted with groups such as those listed above, but a carbon atom adjacent to a nitrogen atom should not be substituted with an hydroxyl group nor should any diazacycloalkene be substituted with a group giving a 'diazacycloalkene free base which, when dissolved in water, gives a hydrogen ion concentration greater than 10- moles per liter.

For the preparation of preferred compounds useful as regulators of the cardiovascular system, the aromatic ring of the tetrahydroisoquinoline compoundfimay be unsubstituted or substituted with chlorine, bromine or. iodine, hydroxyl, alkyl or alkoxy groups containing up to four carbon atoms. The partially reduced ringmay be unsubstituted or substituted with alkyl groups containing up to four carbon atoms. The number four or five carbon atoms of the diazacyclopentene ring may be unsubstituted or substituted with alkyl groups containing up to four carbon atoms as may be the number four, five and six carbon atoms of the diazacyclohexene ring. In addition, the number five carbon atom of thediazacyclohexene ring may also be substituted with an bydroxyl group. 7

It is apparent, therefore, that the tetrahydroisoquinolines ofthis invention can be defined as 1,2,3,4-tetrahydroisoquinolines free of acid substituents giving rise to l,2,3,4-tetrahydroisoquinolines having a hydrogen ion concentration greater than 10- moles per liter in aqueous solution. The diazacycloalkenes can be defined as acid addition salts of 2-alkylthio or 2-ara1kylthio-1,3- diazacyclopentenes or -hexenes free of substituents giving rise to diazacycloalkene free bases having a hydro gen ion concentration greater than 10' moles per liter in aqueous solution, the carbon atoms of said diazacycloalkenes being free of hydroxyl groups when adjacent to a nitrogen atom, the alkyl or aralkyl groups ofv said diazacycloalkenes containing up to ten carbon atoms.

In accordance with the process of this invention, substantially equimolar portions of the selected tetrahydroisoquinoline and diazacycloalkene acid addition salts are reacted in a solvent such as a lower alkanol containing up to six carbon atoms, or a ketone containing up to six carbon atoms. Examples of'suitable solvents include methanol, ethanol, hexanol, acetone, methyl isopropyl ketone and methyl isobutyl ketone. There is no chemical advantage in using an excess of either reactant and it is not necessary to do so.

The temperature and time of the reaction are not criti cal but optimum yields are generally obtained if the reaction mixture is maintained at from about-50 to C. for a period of about fifteen minutes to three hours. It is generally most convenient to select a solvent whose reflux temperature is between the optimum temperature limits and to reflux thereaction mixture for about one hour. During the reflux period the desired product forms as an acid addition salt and occasionally precipitates from the solvent. Precipitation can be enhanced by cooling, lfor example, in an ice bath, or by'the addition of ether.

If a therapeutically active free base'of an acid addi* tion salt prepared as described above is desired, the acid addition salt can readily be converted to the free base by treatment with an alkaline reagent For example, the acid addition salt can be dissolved in Water and-the solution neutralized or preferably made alkaline with base, or the acid addition salt can be taken up in an equivalent amount or preferably an excess of aqueous base. In any case, the active free base can be isolated from aqueous solution by extraction with a suitable solvent preferably a hydrocarbon or halogenated hydro carbon solvent containing up to seven carbon atoms such as chloroform, benzene, toluene, hexane, carbon tetrachloride or methylene chloride. Evaporation of the sol vent, preferably after drying over an anhydrous drying agent such as sodium sulfate, leaves the desired productas aresidue. Suitable alkaline reagents which can be employed in preparing a' free base of this invention include oxides, hydroxides, carbonates and bicarbonates (if the alkali metals and alkaline earth metals sodium hydroxide, potassium carbonate, barium hydroxide and calcium hydroxide.

' The yields obtained in practicing the invention in aceordance with the description given above were generally of the order of 80 to 90%. However, attempts to employ the process of the invention in the preparation of tetrahydroquinoline compounds, that is, to isomers of tetrahydroisoquinoline were unsuccessful.

The following examples are given by way of illustration only and are not to be construed as limitations of the invention, many apparent variations of which are possible without departing from the spirit or scope thereof.

EXAMPLE I 2 -11 ',2,,3,4-tetrqhydro-2 '-is0quin0lyl) 1,3-diazacyclopentene hydrochloride excess of. methyl chloride-while agitating the suspension.

The treatment with methyl chloride was continued intermittently over a period of three days during which time the, 1,3-diazacyclopentane-Z-thione dissolves. The reaction is carried out at room temperature and at the end of three days the solvent is removed in vacuo to give the dcsiredproduct; M. P. 171 to 172.6 C.

Amixture of 0.1 mole of the hydrochloride prepared as. described above and 0.1 mole of 1,2,3,4-tetrahydroisoquinolinein 150 cc. of methanol was refluxed for one hour. The. resulting mixture was cooled in an ice bath and the hydrochloride which precipitated recovered by filtration. It was washed with cold methanol and dried; M. P. 172.8 to 173.6" C. The yield was 88%. An analytical sample was prepared by recrystallization from methanol.

Anqlysis..-Calcd.' for C H N Cl: C, 60,62; H, 6.78; N 17.68; C1, 14.92. Found: C, 60.10; H, 6.84; N, 18.28; C], 15.2.

EXAMPLE II 2(1 ',2',3 ',4'-tetrahydro-2 '-is0quin0lyl 1,3-diazacyclopentene A mixture of 0.1 mole of 2-methylthio-1,3-diazacyclopentene hydriodide and 0.1 mole of 1,2,3,4-tetrahydroisoquinoline in 150 cc. of methanol was refluxed for one hour. The resulting mixture was cooled in an ice bath and the hydriodide which precipitated recovered by filtration. It was washed with cold methanol and-dried; M. P. 186 to 188 C. The yield was 85%. An analytical sample was prepared by recrystallization from ethanol.

Analysis.-Calcd. for. C H N I: C, 43.79; H, 4.90; 1,158.55. Found: C, 44.06;'H,-4.79; I, 38.73.

The free base was obtained by neutralizing an aqueous solution of the hydriodide with aqueous potassium carbonate, extracting the aqueous solution with methylene chloride and removing the organic solvent in vacuo; M. P. 126 to 127 C.

EXAMPLE III 2-(6,7-dimethoxy:1',27,3',4'-tetrahydr0-2' isoql l inolyl) 1,3-diazacyclpentene hydrobrom ide A mixture of 0.1 mole of 2-methylthio-1,3-diazacyclopentene hydrobromide and 0.1 mole of 6,7-dimethoxy- 1,2,3,4-tetrahydroisoquinoline in 150 cc. of methanol was refluxed for one hour. The resulting mixture was cooled inanice bath. and the hydrobromide recovered by filtration.v It .WZiS/WZtShfid with cold methanol and dried; M. P. 261.4 to 262.0 C. The yield was 87%. The

analytical sample was prepared by recrystallization from methanol.

Analysis.-Calcd. for C I-I O N Br: C, 49.1; H, 5.89; N, 12.3. Found: C, 48.9; H, 5.87; N, 12.4.

EXAMPLE IV 2- (3-ph enyl-6'-methoxy-1 ,2',3',4'-tetrahydr0-2'- isoquinolyl) -1,3-diazacyclohexene A mixture of 0.1 mole of 2-benzylthio-1,3-diazacyclohexene hydrochloride and 0.1 mole of'1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline in 150 cc. of hexanol was maintained at a temperature of for two hours. The resulting mixture is cooled in an ice bath and the hydrochloride recovered by filtration. The yield of dry product was 9.1%.

EXAMPLE VI 2- (1 '-phenyl-6,7'-dimeth oxy-1,2',3Z4'-tetrahydro-2'- isoquinolyl) 4-methyl-1.,3-diazacyclapentene A mixture of 0.1 mole of 2-'propylthio-4- methyl-1,3- diazacyclopentene nitrate and 0.1 mole of 1-phenyl-6,7- dimethoxy-1,2,3,4-tetrahydroisoquinoline in 100 cc. of methyl isobutyl ketone was refluxed for fifteen minutes. The resulting mixture was cooled in an ice bath and the nitric acid addition salt recovered by filtration. The yield was 87%.

The free base was obtained by neutralizing the aqueous solution of the acid addition. salt with aqueous potassium hydroxide, extracting the aqueous solution with benzene, drying over anhydrous, sodium sulfate, filtering and removing the organic solvent in vacuo.

EXAMPLE VII A mixture of 01- mole of 2-butylthio-1,3-diazacyclohexene hydrobromide. and 0.1 mole of 6,7-dimethoxy- 1,2,3,4-tetrahydroisoquinoline in cc. of ethanol was refluxed for thirty minutes. The resulting mixture was cooled in an ice bath and the hydrobromide recovered by filtration. It was washed with cold methanol and dried.

The free, base was. obtained by neutralizing the aqueous solution of theacid addition salt with aqueous sodium hydroxide, extracting. the aqueoussolution with benzene. drying over anhydroussodium sulfate, filtering and removing the organic solvent in vacuo.

EXAMPLE vnr 2- (1 ,2',3,4'-tetrahydro-2'-isoqztin0lyl) l ,3-diazacycloh exene-Z A mixture of.0.1 mole of 2-benzylthio-1,3-diazacyclohexene nitrate and 0.1 mole of l,2,3 ,4-tetrahydroisoquinoline in 150 cc. of methanol wasrefluxed'for two hours.

and the nitrate. recoveredby filtration. I

The free base was obtainedbyneutralizing an aqueous solution of, the acid addition salt with aqueous po- The resulting mixture, iscooled in an ice bath tassium carbonate, extracting the aqueous solutioirwith EXAMPLE XI 2-(1 ',2,3 ',4'-tetrahydr0-2'-isoquinolyl) -4,5,6-trierhyl-1,3-

diazacyclohexene-Z hydrochloride A mixture of 0.1 mole of 2-methy1thio-4,5,6-triethyl- 1,3-diazacyclohexene hydrochloride and 0.1 mole of 1,2,3,4-tetrahydroisoquinoline in 15 cc. of methanol was refluxed for three hours. The resulting mixture is cooled in an ice bath and the hydrochloride recovered by filtration.

hexane, drying over anhydrous sodium, sulfate; filtering EXAMPLE XII A mixture of 0.1 mole of Z-methylthio-l,3-diazacyclohexene hydrobromide and 0.1 mole of 3-ethyl-l,2,3,4- tetrahydroisoquinoline in 150 cc. of methanol was refluxed for one hour. The resulting mixture is cooled in an ice bath and the hydrobromide recovered by filtration.

EXAMPLE XIII 2-(1 ',2',3,4-tetrahydro-3'-butyl-2'-isoquinolyl) -1,3-

diazacyclohexene-Z hydrochloride A mixture of 0.1 mole of 2-propylthio-L3-diazacyclohexene hydrochloride and 0.1 mole of 3-butyl-1,2,3,4- tetrahydroisoquinoline inl50 cc. of ethanol was refluxed for one hour. The resulting mixture is cooled in an ice bath and the desired hydrochloride precipitated by the addition of ether and is recovered by filtration.

EXAMPLE XIV A mixture of 0.1 mole of Z-methylthiO-S-hydroxy-1,3-

. diazacyclohexene sulfate and 0.1 mole of 1,2,3,4-tetrahydroisoquinoline in 100 cc. of ethanol was refluxed for three hours. The resulting mixture is cooled in an ice bath and the sulfate recovered by filtration.

EXAMPLE XV 2-(1',2',3',4'-tetrahydro-6-butoxy-2'-isoquinolyl) -1,3-

diazacyclohexene-Z hydrochloride A mixture of 0.1 mole of Z-methylthio-1,3-diazacyclohexene hydrochloride and 0.1 mole of 6-butoxy-1,2,3,4- tetrahydroisoquinoline in 100 cc. of ethyl isopropyl ketone was maintained at a temperature of 75 for three hours. The resulting mixture is cooled in an ice bath and the hydrochloride recovered by filtration.

, sava es 6 AMPLE VI I 2 -l1',2',3',4*-ttrahydro-T-isoquinolyl)-4-bntyl-1,3 diazacyclopentene-Z hydriodide A mixture of 0.1 mole' of 2 -methylthio-4-butyl-L3- diazacyclopentene hydriodide and 0.1 mole of 1,2,23,4- tetrahydroisoquinoline in 150 cc. of methyl isobutyl ketone was refluxed for fifteen minutes. The resulting mixture was cooled in an ice bath and the hydriodide recovered by'filtra'tiom .EXA 2-( 1 ',2',3,4'-tetrahydro-2'-isoquiriolyl) -5-butyl-1,3- diazacyclohexene-Z nitrate A mixture. of 0.1 mole! of 2-rnethylthio-5-butyl-1,3-diazacyclohexene nitrate and0.1 mole'of 1,'2,3,4-tetrahydroisoquinoline in 15.0 ccl of pentanol was maintained at a temperature of 65 for two. hours. The resulting mixture is cooled in an ice bath and the nitrate recovered Yfiltra'tions EXAMPLE XVIII 2-(1',2',3',4'-tetrahydro-3'-butyl-2'-is0quin0lyl) -1,3- diazacyclopentene-Z hydrobromide A mixture of 0.1 mole of 2-methylthio-l,3-diazacylopentene hydrobromide and 0.1 mole of 3-butyl-1,2,3,4- tetrahydroisoquinoline in 150 cc. of ethanol was refluxed for one hour. The resulting mixture is cooled and the hydrobromide recovered by filtration.

EXAMPLE XIX 2-(-] ',2 ',3 ',4'-tetrahydro-6',7'-dibr0m0-2'-isoquin0lyl 1,3-diazacyclopentene-2 sulfate A mixture of 0.1 mole of 2-methylthio-1,3-diazacyclopentene sulfate and 0.1 mole of 6,7-dibromo-1,2,3,4-tetrahydroisoquinoline in 150 cc. of methanol was refluxed for three hours. The resulting mixture is cooled in an ice bath and the desired product precipitated by the addition of ether.

EXAMPLE XX 2-(1',2',3',4'-tetr ahydro-6'-iodo-2'-isoquin0lyl) -1,3- diazacyclopentene-Z hydriodide A mixture of 0.1 mole of Z-methylthio-l,B-diazacyclopentene hydrochloride and 0.1 mole of 6-iodo-1,2,3,4- tetrahydroisoquinoline in 150 cc. of ethanol was refluxed for one hour. The resulting mixture is cooled in an ice bath and the hydriodide recovered by filtration.

EXAMPLE XXI 2-(1 ,2',3 ',4'-tetrahydro-6',7'-dichloro-2'-isoquinolyl) 1,3-diazacyclopentene-2 acetate 9 mixture of 0.1 mole of -2-methylthio-1,3-diazacyclopentene acetate and 0.1 mole of 6,7-dichloro-1,2,3,4,- tetrahydroisoquinoline in 150 cc. of acetone was refluxed for three hours. The resulting mixture is cooled in an ice bath and the acetate recovered by filtration.

EXAMPLE XXII 2- (1',2',3',4-tetrahydr0-6'-ch loro-2'-isoquiriolyl) -5-ethyl- 1,3-diazacyclohexene butyrate A mixture of 0.1 mole of 2-methylthio-5-ethyl-1,3-diazacyclopentene butyrate and 0.1 mole of 6-chloro- 1,2,3,4-tetrahydroisoquinoline in cc. of methyl ethyl ketone was refluxed for two hours. The resulting mixture is cooled in an ice bath and the butyraterecovered by filtration.

7 What is claimed is; 1. The process which comprises reacting a compound ofthefomiula v 5 wherein R is selected front the group consisting-of fllk'yla v mlk l un w- 9 q s ms R5 #14 swash se ected mmthe sm g c n i g Qt Ydmm.

and alkyl containflg up to 4931139]; atoms, R is selected from the group consisting 9; hydrogen, alkyl containing up to 4 carbon atoms and hydroxy, n is an integer from 0 to Land X isqan anion ofanacid selected from the group consisting; of inorganic acids having a hydrogen ion concentration. of at least 107- mols/liter in an aqueous solution, acetic" acid and butyric acid in the presence of a solvent selected from the group consisting of alkanols and ketones containing up to 6 carbonatoms,

2. The processof clairn' 1 wherein the reaction time isfrorn ISminutes to 3 hours.

3. The process of claim 1 wherein the reaction temperature is from 50 to 150 C. I

4. The processof claim 1 wherein R is methyl.

References Cited in the file of this patent STATES- PATENTS 1,91 ,859 Kmnzlcin June 6, 1933 

1. THE PROCESS WHICH COMPRISES REACTING A COMPOUND OF THE FORMULA 